Modeling and Performance Analysis of a Quad Detector

Abstract

In this paper we are interested in modeling, performance evaluation, and measurement of a quadrant detector. Photodiode is modeled using its differential equations then implemented and solved using ORCAD-pspise. The model validation was performed by comparing the model results with the experimental measurements using a proposed setup. The model was used to investigate the effect of the photodiode donor concentrations, acceptor concentrations and intrinsic region concentrations. The simulation results showed that the donor concentrations should be kept as small as possible in order to improve the photodiode performance, the acceptor concentrations has a small effect on the performance, and as the intrinsic region concentration increases the photocurrent increases and the junction capacitance decreases with a small increase in the dark current.

Developing Laser Spot Position Determination Circuit Modeling and Measurements with a Quad Detector

“…Now we will use the full circuit diagram for the laser spot position determination. Starting with the photodiode model [1], [2], [10], [11] and including the preamplifier circuit, the gain circuit, the inverse amplifier, and the ADC. The analog signal output from each section of the 4 quadrant detector is to be read from the microcontroller to make the processing on the signal and provide X and Y position of the laser spot.…”

“…Figure (8-c) show the output of the four photodiode after the inverse amplifier, the positive output due to the ADC work on the positive signal. for the position information, we take the output from ADC and make processing on it to calculate the Y and X equations for laser spot determination according to equation (1) and (2). Figure (8-d) show the output value of X and Y for this condition X=0 and Y= -ve value due to spot center shifted in the negative Y with the detector center.…”

“…segments, separated by a small gap, called the dead region. In QD the position is extracted by comparing each segment's photocurrent [1], [2].…”

Modeling and Measurements of Laser Spot Position Determination Circuit with a Quad Detector

“…Starting with the photodiode model [1,2] and including the preamplifier circuit, the gain circuit, the inverse amplifier, and the ADC. The analogue signal output from each section of the 4 quadrant detector is to be read from the microcontroller to make the processing on the signal and provide X and Y position of the laser spot.…”

“…Figure (7-b) shows the output of the four photodiode after the amplifier, the output is the same. Figure (7-c) shows the output of the four photodiode after the inverse amplifier, the positive output is needed since the ADC works on the positive signal, for the position information we take the output from ADC and make processing on it to calculate the Y and X equations for laser spot determination according to equation (1) and (2). Figure (7-d) shows the output value of X and Y for this condition X=Y=0 due to spot center with the detector center.…”